Rechargeable batteries comprising battery cells of the lithium-ion (Li-ion) or nickel-metal hydride (Ni-MH) type, or similar, have become increasingly used as an energy source for powering electrical vehicles and other devices, such as boat engines and cleaning machines, as well as for powering e.g. cellular network base stations in remote areas.
In such applications, several battery cells are connected in series and/or parallel in a battery module such as to be capable of delivering the required power. In order to be able to deliver the required power and to limit the energy losses, the battery cells are normally connected in series such that a high voltage battery is obtained. The high voltage battery is connected to the electrical system of the vehicle through positive and negative output terminals.
There is a need to monitor different properties of the high voltage (HV) battery, such as the voltage over the output terminals, the total current delivered by the battery, the temperature of the battery etc. Some of these properties can be measured and estimated by the battery itself and other on-board systems of the vehicle. For some measurements, the on-board measurements cannot be used. Instead, actual “live” measurements are required.
One such occasion is when measuring driving cycles for the electrical vehicle. When the vehicle performs a driving cycle according to the New European Driving Cycle (NEDC), which is supposed to represent the typical usage of a car in Europe, it is important that the voltage and the current delivered by the battery is measured outside of the vehicle, with separate measurement equipment. Other situations when external measurement equipment is of advantage is e.g. when the vehicle is in a work shop for maintenance.
During such a test, a separate current clamp is used for each positive or negative output terminal and separate clamps are also used to measure the voltage of the battery. There is thus room for an improved battery measuring arrangement.